Description of problem:
waybar segfault since 0.13.0 upgrade

Version-Release number of selected component (if applicable):
waybar-0.13.0-1.fc42.x86_64

How reproducible:

unsure, but happened a dozen of times today...

Actual results:

segfault that looks like this
```
(gdb) bt full
#0  Gdk::Pixbuf::gobj (this=<optimized out>) at ../untracked/gdk/gdkmm/pixbuf.h:389
#1  Gdk::Pixbuf::get_height (this=0x0) at ../untracked/gdk/gdkmm/pixbuf.cc:522
#2  0x0000560ca80df364 in waybar::modules::SNI::Item::updateImage (this=this@entry=0x560ca938d6f0)
    at /usr/include/glibmm-2.4/glibmm/refptr.h:259
        pixbuf = {pCppObject_ = 0x0}
        scaled_icon_size = 16
        surface = {pCppObject_ = 0x0, pCppRefcount_ = 0x7}
#3  0x0000560ca80dfa98 in waybar::modules::SNI::Item::proxyReady (this=0x560ca938d6f0, result=<optimized out>)
    at ../src/modules/sni/item.cpp:106
        cached_properties = {size_ = 13, parray_ = 0x560ca9391a10, ownership_ = Glib::OWNERSHIP_DEEP}
#4  0x00007fb9a20d3c1e in sigc::slot1<void, Glib::ustring const&>::operator() (this=0x560ca938a6d0, _A_a1=...)
    at /usr/include/sigc++-2.0/sigc++/functors/slot.h:675
#5  Gio::SignalProxy_async_callback (res=<optimized out>, data=0x560ca938a6d0) at ../gio/giomm/slot_async.cc:32
        result = {pCppObject_ = 0x560ca938d670}
        the_slot = 0x560ca938a6d0
#6  0x00007fb9a15b2e7c in g_task_return_now (task=0x560ca91d9890) at ../gio/gtask.c:1363
#7  0x00007fb9a15b8590 in g_task_return (type=<optimized out>, task=0x560ca91d9890) at ../gio/gtask.c:1432
        source = 0x7fb9880073b0
#8  g_task_return (task=0x560ca91d9890, type=<optimized out>) at ../gio/gtask.c:1389
        source = <optimized out>
        source_name = <optimized out>
#9  0x00007fb9a1626dd0 in init_second_async_cb
    (source_object=0x560ca938e580, res=<optimized out>, user_data=0x560ca91d9890) at ../gio/gdbusproxy.c:1757
        task = 0x560ca91d9890
        error = 0x0
#10 0x00007fb9a15b2e7c in g_task_return_now (task=0x560ca938ede0) at ../gio/gtask.c:1363
#11 0x00007fb9a15b8590 in g_task_return (type=<optimized out>, task=0x560ca938ede0) at ../gio/gtask.c:1432
        source = 0x7fb9880073b0
#12 g_task_return (task=0x560ca938ede0, type=<optimized out>) at ../gio/gtask.c:1389
        source = <optimized out>
        source_name = <optimized out>
...

Expected results:

no segfault

Additional info:

This is https://github.com/Alexays/Waybar/issues/4231 already fixed upstream

People already asked for a 0.13.1 but since there is none could https://github.com/Alexays/Waybar/pull/4234/commits/460b19ba1b83b873795e2e65ce60efadc7a3a906 be backported?

Thanks